Or you can use them to prove that carbon dioxide DOES strongly affect global temperatures:

Carbon dioxide and temperature, past 150 years. From http://www.climatechoices.org.uk/pages/cchange3.htm

What’s going on here?

For starters, both presentations are tricking you. Carbon dioxide is not the only factor affecting global climate, nor is carbon dioxide so inert as to have no effect whatsoever. Indeed, it is almost impossible to find a graph such as this that is not trying to trick you in some way.

So I’m going to produce a graph you can trust, one with no tricks whatsoever.

What can we hope to learn from such a graph? We can hope to learn whether it is plausible, from a cursory examination of the data, whether carbon dioxide might be a significant factor in global climate change. We can’t actually prove anything, because there are many factors that affect climate. However, if all the theory, calculations, and models are right, and carbon dioxide is a major factor in climate change, we should at least expect recent changes in climate to be in the same ballpark as the sort of climate changes to be expected from carbon dioxide increases. Graphing up CO2 and temperature and comparing them is a smell test, nothing more.

For a point of departure, I’ll take this particularly egregious graph, which I encountered recently:

Carbon Dioxide and Temperature, 2002-2009

The temperatures, in blue, are (I think) an earlier version of UAH MSU global mean lower tropospheric temperatures, and the dashed blue line is a best-fit trend. The temperature scale is on the left. In green is carbon dioxide concentration, in parts per million, seasonal cycle removed, with the scale on the right.

Both data sets are plotted accurately. So what’s wrong?

What’s wrong is the implication that the blue line (or dashed blue line) ought to in some sense match up with the green line. It is true that rising CO2 should imply rising temperature, but how much should those temperatures rise?

The global temperature change is expected to be proportional to the change in the logarithm of CO2 concentrations. This is where most such graphs, including all the examples above, fall flat. They plot CO2 on a linear scale, as though CO2 concentration and temperature ought to be related linearly. Instead, radiative transfer theory tells us that they ought to be related logarithmically.

Furthermore, mainstream climate science has an estimate for how big an effect a logarithmic CO2 increase ought to have on global temperatures. Most estimates for equilibrium climate sensitivity are somewhere around 3 C for a doubling of CO2 concentrations, give or take a degree or so. However, that’s the estimate for overall temperature change once the oceans have equilibrated to the new CO2 concentration, and that’s expected to take hundreds or thousands of years. The instantaneous response is thought to be somewhere around half that. So, given the CO2 increases that have taken place since the industrial revolution, the expected response to those increases ought to be between 1.5 C and 3.0 C per CO2 doubling.

The actual response will vary, because there have been other Tyndall gas increases, plus solar intensity has changed, plus aerosol concentrations have increased. Also, the response of lower tropospheric temperatures ought to be slightly larger than the response of surface temperatures, according to computer models. But hey, at least we can plot the actual temperature change against the temperature change expected from CO2 concentration increases. This will be an apples-to-apples comparison, while most other such graphs have been apples-to-oranges. To make it fully apples-to-apples, I’ll plot both the expected and actual temperature changes as anomalies relative to the 1981-2010 base period (the UAH data comes that way already).

The red line shows the expected immediate response from CO2 forcing, while the blue line shows the expected long-term response from CO2 forcing. They show that CO2 forcing wasn’t supposed to be causing a dramatic temperature rise over this 7.5-year period after all! Instead, given how much CO2 concentrations have increased, it should only be responsible for about 0.05-0.1 C of warming.

Still, it’s true the CO2 has been going up, while the temperature trend is downward. One useful application of trend analysis is to forecast future values, so let’s see which is more useful for predicting later values of global temperature, the observed 2002-2009 temperature trend, or the sensitivity to CO2 changes:

Temperature and CO2 forcing, 2009-2012, with linear regression from 2001-2008.

It looks like recent temperatures have been averaging about 0.2-0.3 C above the 1981-2010 mean. If you made a prediction using the increasing CO2 concentrations, you slightly underestimated the warming were fairly accurate. If you made a prediction using the 2002-2009 observed trend, you were way off.

Let’s put the two periods together:

Temperature and sensitivity to CO2 forcing for period 2002-2012

It didn’t take too long for the observed trend to reverse itself. Over this longer period, it’s positive, but still it’s a lot weaker than what would be expected from the increasing CO2 concentrations.

But wait a minute. You don’t suppose the starting date of 2002 was a cherry-pick, do you? Let’s see what happens if we start at the beginning of the millennium:

Temperature and CO2 sensitivity, 2000-2012

Wow, the observed trend is right there in the range of what would be expected from the change in CO2 concentrations alone! But maybe now I’m cherrypicking with a starting date of 2000? Okay, let’s plot the full data UAH lower tropospheric data set:

Temperature and CO2 forcing, UAH MSU period of record

The period of record linear temperature trend almost perfectly matches the temperature trend expected from CO2 concentration increases at equilibrium. This almost-perfect fit is surely an accident, because of all the other factors discussed above. But at least The period of record linear temperature trend lies between the temperature trend expected from transient CO2 climate response and the trend expected from a long-term equilibrium climate response. We can confirm that the amount by which observed global temperatures HAVE changed since 1978 is in the same ballpark as the amount by which global temperatures SHOULD HAVE changed, if current estimates of climate sensitivity are correct.

If you plot other data sets, you’ll get slightly different results, but the same take-home message: there’s nothing in recent global temperatures that disproves the importance of CO2 as an agent for climate change.

51 Responses

Is not the reason for the good fit to CO2 simply that the net forcing from all human activities is pretty much the same as the CO2 forcing by itself. See the Figure 2.1 on page 136 of http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter2.pdf. In that case the fit of CO2 to temperature isn’t an unexpected result (although the fact that the nonCO2 forcings should cancel out is)

” But at least we can confirm that the amount by which observed global temperatures HAVE changed since 1978 is in the same ballpark as the amount by which global temperatures SHOULD HAVE changed, if current estimates of climate sensitivity are correct.”

This is a much more reasonable ballpark than just showing concentration vs. temperature, but I would argue that the biggest thing you’re missing is that you should also expect lagged warming from previous emissions… eg, if we managed to hold CO2 at a constant concentration for the next 10 years, you’d still expect to see some warming over that time. The longer the time period you’re looking at, the less this will matter, though (eg, if you did the full 20th century, you’d have very little lagged warming from increases in the 19th century…)

Put two one thousand pound sumo wrestlers on a seesaw and it goes nowhere. Given a frictionless axle and placing a feather on one end would make that end go down.

Same for the climate. One wrestler’s name is cooling forcing agents, the other warming forcing agents. On average the resulting “seesaw” would wobble. However add just a smidgen more at one end or the other and that end would go down.

John, you present an interesting illustration of lying with numbers and graphs. Bravo!

However, I humbly submit you may be guilty of it yourself, however inadvertently. If you really want to pass the smell test, plot the uncertainty limits on your regression, and also the uncertainty limits on the CO2 sensitivity curves, as well.

I haven’t take the time to do so myself, but visual examination of the input temperature data suggests the regression uncertainty limits may exceed the total variance of the CO2 sensitivity predictions. In other words, it’s possible the regression is statistically meaningless. I’d really like to know, one way or another.

Also, have you applied your analysis to the entire “hockey stick graph” time range? I’d be very interested to see the result.

Uncertainty limits are only useful for hypothesis testing. The hypothesis I am testing is whether the observed temperature rise is of a magnitude consistent with the magnitude expected from CO2 forcing. Conventional uncertainty limits would be appropriate for a much stricter hypothesis, that the observed temperature rise is caused entirely by CO2 forcing. I do not put forward that hypothesis because I know it to be incorrect. There are many other forcing factors at work. For similar reasons, the data plots should not be used to infer which CO2 climate sensitivity curve is correct. Any statistical agreement would be fortuitous, and I think it would be misleading to show sensitivity ranges that imply that a statistical agreement would be meaningful.

I don’t know your preference for a reconstruction, but for CO2-driven temperature change, using a preindustrial concentration of 270 ppm and a present-day concentration of 395 ppm, the corresponding temperature rise would be 0.8 C for a transient sensitivity of 1.5 and 1.6 C for an equilibrium sensitivity of 3.0.

John, in that case, it might be appropriate to modify your closing sentence from:

“If you plot other data sets, you’ll get slightly different results, but the same take-home message: there’s nothing in recent global temperatures that disproves the importance of CO2 as an agent for climate change.”

to:

“If you plot other data sets, you’ll get slightly different results, but the same take-home message: there’s nothing in recent global temperatures that [either proves or] disproves the importance of CO2 as an agent for climate change.”

I can’t pretend to be any kind of climatologist, but I do have an academic background in stable isotope geochemistry and mathematical modeling, so I tend to be a bit phlegmatic about all the climate change hoopla. “Climate” changes on the timescale of a human lifetime are insignificant in any geologic timeframe. Just as you can cherry pick any five or ten year span within the 34 year dataset and come up with any desired regression slope, you can do the same with any 30 or 40 year time span in the past millenium. Dittos for any 1,000 year time span in the Holocene.

That’s not to say we shouldn’t be doing everything we can to study potential anthropogenic climate forcing. Geologically speaking, the rise of industrial humans is a singular event. As the Alvarez team so convincingly demonstrated, singular, geologically instantaneous events can have a rather profound impact. (Geo-pun intended.) But it seems prudent to avoid making any sweeping, and potentially economically harmful, policy changes based on the predictions of a science that is still in its infancy.

Data from the UK Meteorology office leaves little doubt that global temperature has not followed CO2 for most of the last two decades. That was, in fact, the picture for most of the twentieth century, before 1980. This confirms that CO2’s influence is tiny, overwhelmed by other factors that do control global temperature, as can be seen in this lecture:

Salby is a deeply confused man who doesn’t understand that even though ENSO controls the interannual variability, there is absolutely no doubt whatsoever that human anthropogenic CO2 emissions have contributed to the bulk of the observed CO2 increase over the past 200 years. And there’s been no doubt on this point for decades. This was a solved problem about half a century ago.

It’s worse, MMM: it appears Salby is *willfully* misleading his audience. Just see this write-up of Tom Curtis:http://www.skepticalscience.com/salbyratio.html
Now, one can argue with Curtis’ simplification of an isomorphic relationship. But even without that, Salby did a clearly deliberate rescaling to exaggerate the supposed divergence. The type of graphical misrepresentation John discusses above.

Thanks for fixing the graphs. First try didn’t look quite right…. because it matched the ECS = 3 a bit too closely. Now it looks closer to 2, which better matches other empirical estimates. Not far off from your ECS = “e” guesstimate of AWB.

I know, there’s lot’s of other stuff going on here, too. Still, for empiricists, this seems a decent data-point. Call it “equivalent Climate Sensitivity”. And wait for Pielke Sr. to weigh in.

Who knows, maybe he’d swallow an equiv-CS estimate as a proxy for all the land-use and other stuff he properly points out are being done by Modern Industrial Humankind…. as is so vividly demonstrated when you look out the airplane window (etc).

The long term global warming trend since the Little Ice Age has not accelerated [in fact it seems to have stalled]. The long term warming trend is the same, whether CO2 is low or high. Therefore, CO2 has no measurable effect on temperature.

“The long term global warming trend since the Little Ice Age has not accelerated [in fact it seems to have stalled].”

Once again, confusing short- and long-term trends: did this putative ‘long-term trend’ stall during the temperature decline of the 60s, or indeed during the decline around the turn of the 20th century? Global temperature is a noisy data set, and drawing long-term conclusions from ten or fifteen years worth is going to mislead–as indeed this post demonstrates.

There’s nothing in the recent global temperatures that disproves the importance of CO2 pixies as an agent for climate change.

Good grief man, your logic is bass ackwards. It’s a load of carp. How about proving that the recent warming is NOT of natural causes. That would be an effective argument. You can’t can you? That’s why you argue backwards.

It is logically impossible to prove a negative. At this point, it is obvious that the warming is partly human-caused, and for the most part it has the size and basic pattern that Tyndall gases would be expected to produce.

John:
I see that (per Google) your use of “Tyndall gases” to replace “greenhouse gases” hasn’t caught on yet (Hit #6 directs readers to “Find Cheap Gas Prices in Tyndall, South Dakota”). So I’m supposing you mean (comparatively) long-lived gases such as CO2 and methane, as opposed to water vapor?? Your first article on this refers, even less transparently, to “EFKAG”, which I now see is the “effect formerly known as greenhouse.” OK!

You’re right, of course, that the “greenhouse effect” has nothing to do with actual greenhouses, but I thought a translation note might help new readers. And I suspect your Tyndall gas campaign will have very limited success….

Cheers — Pete Tillman
–
“The trouble with predicting the future is that it is very hard.”
– Yogi Berra

Unless there is a truly massive methane release that wipes out the oxidizing capacity of the atmosphere (unlikely), methane is not particularly long lived, even as compared to CFCs (~100 yrs or so), CO2 hundreds to thousands of yrs, or SF6, essentially forever)

“Planetary nebula” — for the halo of ionized gas blown off in a supernova explosion. Planets are not involved — except, possibly, as vaporized portions of the cloud. But generations of newcomers are misled….

“Metals” in astronomy (specifically, optical spectroscopy) are any elements heavier than hydrogen & (ims) helium — leading to the the rather mind-boggling (to a chemist) description of nitrogen, carbon, argon, and various other emphatically non-metallic light elements being called “metals.”

At least in geology, we have (more or less) done away with “ultrabasic” rocks (exceptionally high in iron, magnesium and manganese, and once thought to be chemically basic) which are now “ultramafic” = very dark in color.

So don’t expect much from “Tyndall gases” — terminology usually locks in pretty early, whether it makes sense later, or not.

Cheers — Pete Tillman
–
Poppycock: did you know this word derives from the Dutch
pappekak, meaning ‘soft crap’? Well, now you do….

James says:
>>Very funny. But some people may not realise that this is intended to be a joke.

john n-g says:
>And the tricks are…?

My answer would be that choosing a century level temperature chart and not subtracting the rebound from the LIA is a ‘trick’, in order to rather conveniently get an upward long trend in both CO2 and temperature.

I am not sure it can be confidently quantified, but to take a trend that includes a definite upward pre-industrial trend and not subtracting it to look for the ‘CO2 influence’ is a little trickier than I thought we would see here.

Otherwise I think you have discussed it well. You could cover the implications on the charts of century scale (pre-existing trends) in CO2 and Temp. I don’t think you have to explain them, but it is fair to include the underlying data.

If CO2 has a lot of effect, we must show a predictable influence with natural variations factored out. I think it is pretty well known that the last 8000 years have not demonstrated the influence. There are lots of data quality isses, but there is no accumulating evidence that CO2 is a major driver. If the claim is CO2 a minor driver, it is pretty easy to argue it is smaller than the noise, which in my lab, at least, does not allow confident conclusions to be drawn.

Equally hilarious, John, is the “rebound from the LIA”. It’s all magic what our climate does, it needs no forcings to change. It just magically goes back to warmer temperatures, because it felt the LIA was a bit chilly…

John….what appears to be missing in all of this that perhaps, just maybe,
an increase in temperature of 2, or3C, might be very helpful. The whole
of the northern hemisphere would have a longer growing season. We
know that SW Greenland people gave up with the LIA, and we’re in
an upward temp trend. And of course, we know with certainty that
CO2 at higher levels helps plant growth and water use.

[...] not sure if the IPCC says that, exactly. This post suggests you need better evidence for number 3: Carbon Dioxide and Temperature | Climate Abyss | a Chron.com blog I never said the lower latitudes were suffering, I say they inevitably will. But some countries do [...]

So there is no problem. Is there? There is only a belief that there might be, could be a problem. Not good enough to shut down modern society. And taxpayers have wasted far too much miney promoting the “carbon” scare.

Given the IPCC estimates of the various forcing magnitudes and uncertainties, I would say that the UAH data constrains equilibrium sensitivity to between 1.0 and 7.0. The climate sensitivity is much more tightly constrained by other lines of evidence; I put it at 2.0 to 4.0.

If manmade CO2 explains the modern warming period, then we are left with no explanation for the warming into the Roman Warm Period or the Medieval Warm period or for the warming into many other warm periods in the past ten thousand years. The temperatures in this modern warm period are well inside the bounds of the past ten thousand years. Only CO2 is outside the bounds of the past ten thousand years and that is strong evidence that temperature does not care very much about what happens with CO2.

Sorry, just cherry-picking some dates that prove your point, as all these graphs above do, does not prove anything objectively. And certainly not convincingly enough to cause massive government action to do anything, this describes it all very well:http://mckaylaisnotimpressed.tumblr.com

In the ice core records, there is much correlation of CO2 levels following up and down with Temperatures. There is a lot of CO2 in the oceans and it is well known basic physics that the vapor pressure of a gas is dependent on temperature. You can read a lot of consensus climate theory and never hear this even mentioned. Consensus climate theory only discusses the uncertain sensitivity of temperature to CO2 and feedbacks but does not mention the well known sensitivity of CO2 to temperature.

Can I assume that you think the CO2 increase is due to the ocean outgassing?

If so, we’re going to have some fun discussions. Better bring your calculator, because it’s going to get messy.

Oh, and you might be surprised to learn that “consensus climate theory” explains the increases in CO2 during interglacials by at least in part outgassing from the oceans. Unfortunately, that amounts to only about 100 ppm for a ca 6 degree Celsius increase over several thousand years, not a 100+ ppm increase for about a 1 degree increase over about a 100 year period.

I’m sorry but that is sheer ignorance. Before we even had accurate ice core samples, the idea of CO2 lagging temperature changes forced by orbital changes was *predicted*. See the following and note the date!

You state that “the gradually rising long term trend line since the LIA is not accelerating”. The graph you link to seems to show central england temperatures rather than global temperatures. Even if we take this as a crude approximation for global temperatures, the liniar trend you apply masks the real change. If you use a moving average you get a clearer picture. The temperature seems to hover around 9C until the turn of the 20th century.

For global land temperatures we can look at the BEST reconstruction. This has a comparison to known volcanic eruptions and carbon dioxide. Is this one also a trick? It seems to fit too well to be true…

“…I would say that the UAH data constrains equilibrium sensitivity to between 1.0 and 7.0. The climate sensitivity is much more tightly constrained by other lines of evidence; I put it at 2.0 to 4.0.”

That is simply an assertion; handwaving. There is NO empirical evidence directly connecting the rise in CO2 with global warming. None at all.

Without any measurable evidence, all you have is an untested conjecture. An opinion. Following a very substantial ≈40% rise in CO2, you should certainly be able to provide ample empirical evidence to support your belief that CO2 causes global warming. But the fact that you have no such evidence argues convincingly that your CO2 conjecture has been falsified by the ultimate Authority: Planet Earth.

Finally, more than 30,000 scientists and engineers — all with degrees in the hard sciences, including more than 9,000 PhD’s — have co-signed the OISM Petition stating that CO2 is harmless and beneficial. THAT is the ‘consensus’, from people who know what they are talking about. Those demonizing “carbon” are in reality a relatively small clique of rent-seeking climate alarmists.

There is no problem with rising CO2. It is harmless, and beneficial to the biosphere. More is better.

Such a chart will be impossible to produce until man has gone through several cycles of adding and removing CO2 from the environment. Presently, we’re just in the middle of our first major anthropogenic increase. Thus, you have asked for something that’s can’t be created for another several thousand years. What would be next best?

If we have to wait several thousand years to see any effect, then there is not a problem, is there?

Without measurements you don’t have a testable hypothesis. You only have a conjecture, and so far the real world appears to be falsifying the “carbon” scare. We are into sixteen years now with no global warming. How many years do you require before you admit your conjecture is fatally flawed?

∆T causes ∆CO2. But there is NO empirical evidence showing the reverse is true. It is possible that the rise in CO2 might cause some minuscule warming. But the effect is so small that it is not even measurable, therefore it can be completely disregarded for all practical purposes.

The “carbon” scare has been falsified. Without empirical measurements showing any effect of CO2 on temperature, it can hardly be called science. The “carbon” scare is simply a false alarm.

One last thought. You mentioned that there is ample evidence that global temperatures are not accelerating.

The graph of Central England Temperatures that you first pointed us towards shows temperatures hovering relatively steady at 9C prior to the 20th century and rising above 10C by 2011. It seems like there must have been some acceleration to get from there to here (Assuming you are right that central england temperatures are a good approximation for global temperatures): http://media-cache-ec3.pinterest.com/upload/354377064398337327_vGBI4hu1.jpg